At the Accelerator Laboratory of the University of Zibaskira in Finland, physicists utilized a gas-filled recoil separator focal plane spectrometer to observe two attenuation events of the newly discovered isotope astatin-188 (188At), which is composed of 85 protons and 103 neutrons.
Kokkonen et al. Report the discovery of the new nucleus 188At, which is the heaviest proton-emitting isotope known to date.
“Proton emission is a rare type of radioactive decay where the nucleus releases protons, moving toward stability,” explained Henna Kokkonen, a doctoral researcher at Zibaskira University.
“This new nucleus is currently the lightest known isotope of astatin, 188At, containing 85 protons and 103 neutrons.”
“Studying this type of exotic nucleus is exceedingly challenging due to its brief lifespan and low production cross-section. Therefore, precise techniques are essential.”
“The nuclei were produced through fusion deposition reactions by irradiating natural silver targets with a 84Sr ion beam,” added Dr. Kare Auranen of Zibaskira University.
“The detection of the new isotopes was made possible using the Ritu Recoil separator’s detector setup.”
In addition to the experimental findings, the physicists expanded theoretical models to interpret the collected data.
According to the team, 188At can be likened to a strong explosion, resembling “the shape of a watermelon.”
“The nuclear properties suggest a shift in the behavior of the binding energy of valence protons,” Kokkonen stated.
“This is attributed to unprecedented interactions with heavy nuclei.”
“Isotopes are rare globally, and this marks the second occasion I’ve had the chance to make history.”
“All experiments pose challenges, and it is rewarding to conduct research that enhances our understanding of the fundamental limits of matter and nuclear structure.”
The authors intend to refine the current uncertainties and half-life of the attenuation energy by further theoretical exploration of charged particle-damped heavy nuclei, observing the evolution of their shapes, and examining additional decay events of 188At.
“Equally intriguing is the study of the collapse of a currently unknown nuclear isotope 189At, which could be a proton-emitting nucleus, an aspect we have yet to explore in future experiments,” they concluded.
Their paper was published in the journal Nature Communications.
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H. Kokkonen et al. 2025. New Proton Emitter 188At signifies unprecedented interactions in heavy nuclei. Nat Commun 16, 4985; doi:10.1038/s41467-025-60259-6
Source: www.sci.news
